Threat of Lyme disease widens

Lyme disease, the tick-borne ailment once primarily a scourge of the Cape and Islands, is now rampant in swaths of Massachusetts where locally acquired cases were rare a decade ago.

In Middlesex, Norfolk, and Worcester counties, the number of patients diagnosed with the bacterial disease surged more than fourfold between 2000 and 2009, according to figures the state Department of Public Health provided to the Globe.

The increase, which is fueling a statewide increase in reports of symptoms, is evident in the offices of infectious disease specialists and primary care doctors in places like Framingham and Natick, where Lyme disease diagnoses 10 or 15 years ago were largely restricted to people who had visited Cape Cod.

“Now,’’ said Dr. Richard Ellison, hospital epidemiologist at UMass Memorial Medical Center in Worcester, “they’re living in Charlton, they’re living in Northborough, they’re living in Westborough. And they’re not traveling to the Cape.’’

The disease is on the move, special ists said, because the deer population is expanding and human developments are encroaching on natural habitats. Hundreds of ticks can hitch a ride on a single deer. And a lone female tick can lay 2,000 — or more — eggs.